1. Field of the Invention
Embodiments of the present invention generally relate to a method and apparatus for testing shear fasteners used in downhole tools.
2. Description of the Related Art
In order to reduce cost of overall production of oil and gas, oilfield service companies have continually sought ways to employ the most accurate and safe equipment in the field. In addition, cost effective ways of deploying and actuating such devices are continually sought. Many of these devices across a number of competitors use a very similar manner to deploy and actuate these devices: shear fasteners.
Shear fasteners serve a dual purpose, they fasten bodies of a down-hole tool together and they must break at a specified value in order to deploy, set, release, or actuate a tool. Because of this function, the shear fastener must shear perpendicular to its axis at a very precise value of pound force.
In order to procure parts that would be known to shear at a precise value of pound force, oilfield service companies have created a number of proprietary shear testing procedures, shear testing devices, and shear fastener designs. Most of these shear testing devices, or testers, are composed of inner and outer sleeves that move in opposite directions. This opposing motion causes the shear force. When procuring these fasteners, the oil and gas service companies approach suppliers who must manufacture according to a number of different procedures and testers. This approach can be very costly.
Ideally, the testers employed by the oil and gas service companies should mimic the operation of their downhole tools. In this way, the test data would accurately reflect downhole operation of the fasteners. However, existing testers are designed for testing fasteners for several different tools. Consequentially, the testers do not accurately represent any particular downhole tool geometrically or functionally. The tester operates in a laboratory environment, whereas the downhole tools have very long and straight slips which restrict lateral movement. Since these downhole tools are manufactured to be very long, the tolerances in between the bodies that make them up are not exacerbated. In this sense, a shorter tester will exacerbate the loose tolerances between the bodies that make it up, resulting in an inaccurate test result.
Additionally, current designs of testers for general use do not have the ability to test a variety of different fastener configurations in an efficient manner.